A SMRU Project

Last month we said our good-byes to the seals as the field season concluded at our study sites in Orkney, Kintyre and Isle of Skye. All teams have taken a well deserved break from the field, and the office work welcomed us back with a big smile. Until the next fieldwork season starts in June of 2019, the time will be mostly spent processing all the pictures collected, meaning our computer screens will most likely show seal faces for the next few months:

Part of the seal catalogue for Orkney, showing the right-hand side of each identified seal

Once the photographs for the season have been processed, we can have a look at what the data shows. We can figure out how many seals were seen, and in the case of adult females, we will have information on whether they had a pup or they did not. Of course it might be that a female had a pup but we just did not see it, let’s say if that female decided to pup nearby instead of the monitored site. By constructing these sighting histories in consecutive summers, we can learn about the mortality and birth rates that characterize each study site, and find out whether there are any differences between areas where the number of seals have been declining (such as in Orkney) or where the number of seals has been stable or even increasing (such as in areas of the West coast).

Sighting histories of some of the females from Orkney in the summer of 2016, between mid May and the end of July. The different colors represent information associated with each sighting. For example a green dot means we photographed the female on its own, a yellow dot it means we could see it was pregnant, and the blue and red dots mean the female had a pup with her.

The pelage of harbour seals comes in all kinds of colors, as the proportion of dark and light colors changes across seals. Some seals are very pale, especially in the head area, while others are very dark. Some of the paler seals are especially difficult to identify given the lack of pelage pattern. It gets even more difficult as the summer advances and the time of the moult gets closer.

Or043 is one of the pale females regularly seen in the Orkney monitored sites

Or094 is also a regularly seen female in Orkney but she has a much darker pelage pattern!

Seals will start the moult at different times, driven by the sex and reproductive status, although other factors will have an influence on the timing of the moult, for example body condition, temperature and hormones. Harbour seal pups moult first in utero, before the birth. After that, yearlings, which are the animals that were born the previous summer, will be the next ones to moult, followed by older seals including juveniles, adult females, and finally adult males. This summer, some of seals in Orkney made a good progress of the moult by the end of July, and a few were showing an almost complete new pelage by the end. Who knows, maybe the hot weather allowed them to moult a bit quicker than other summers. Whichever the reason, one cannot deny they look beautiful once the new pelage shows up, and the contrast with the brown looking pelage of just a few weeks before is noticeable.

This female, seen in Widewall Bay, had only a few remaining patches of the old coat around the flippers and nose by the end of July

Or007 showing clear signs of moult, especially around the head on 8th July this year

Last weekend marked the end of another field season for the project. In Orkney, the vibe at the haulout sites changed significantly during the last week. Most of the pups were observed on their own, and thus likely to be fully weaned, and only a few mum-pup pairs were seen interacting. One of the few left was Or026, which was one of the last ones to pup this year around the 28th or 29th of June, as we explained in this other post.

Or026 in the water with her pup in Orkney

The processing of the photographs from this year is still to be completed, with which we will attempt to identify every seal that has been photographed. Then we can figure out which females pupped this year, information that will be used to estimate birth rates in Orkney as well as at the other study sites. Going out to get the pictures keeps us busy enough, but there is still some basic data processing we have to do everyday after coming back from the field. The photographs have to be renamed with information on where the pictures were taken (because we have several sites that we monitor) and the trip number. Then we have to add the metadata associated to each photograph to a table, so that each row shows all the available information to each photograph. If the photograph shows more than one seal we need to state which seal are we talking about. We can then add information, when available, on whether a female was seen with a pup or alone, on whether suckling was observed, or whether we can tell if a seal is a male or a female from photographs of the genital area.

When a photograph shows more than one seal, we indicate which seal we are referring to by counting the number of seal heads in the photograph and adding the head number for the seal of interest counting from left to right in the frame.

The pups that are weaned or almost weaned look quite massive compared to when they were born, and some of them are so similar in size to the seals born last summer that one needs to triple-check to make sure it is a pup and not a yearling.

Or057 with a rather looking big pup!

Even though the identification of the females that have pupped this summer is still to be completed, we have recognized most of the females. Some of them have pupped for a third consecutive year, including Or094 in Burray, nicked-named “coliflower”, who had her pup on June 19th , and Or044, nicked-named “butterfly”, which is regularly seen in Widewall Bay.

Or094 in the catalogue with her pup in 2016, 2017 and 2018

Or044, “Butterfly”, is regularly seen in Widewall Bay, where she has been seen with a pup for the last three summers

While some pups have been seen suckling from their mums right up until almost the end of July, others that were born earlier in the season were already weaned by then. Some pups have to be a bit more pushy to get the female to lay on its side so that they can suckle. They do so my pushing their nose against the side of mum, until she turns around to get her belly exposed, as does mum Or045 in this video:

The pups that either have already been weaned or might just be spending more time on their own at the haulout sites might still try for a cheeky extra meal if that’s on the offer. In the video below, you can see female Or057 at the haulout sites together with her pup and some other pups. One of them, is trying to slowly approach the female from the the water, but it doesn’t seem that this tactic will work with Or057…

During the last few days of monitoring in Orkney we also noticed an increase in the number of seals starting their annual moult or well into it. More on this in the next post!

Kintyre has seen a fair few new arrivals since we last wrote! Firstly, there have been (at least!) ten new pups, with mum and pup pairs observed at almost all of field sites here in Kintyre. And secondly, the arrival of myself, Emily, as another short term field assistant. I’ve been working with the permanent field assistant here, Izzy, for the previous few weeks to gain experience in the collection of seal photo-ID data and to become familiar with the field sites. I work on maintaining the Kintyre photo-ID database back at SMRU, so it has been a great eye-opener to get out of the office and see the sites, the seals, and to see ‘behind the scenes’ how the data is collected. On my return to SMRU I will now be processing the 2018 photographs, updating the catalogue and adding in any new (very cute!) additions from 2018.

A young pup photographed at Seal Rock (photo: Emily)

During the previous two weeks I’ve seen pups at 4 of the 5 field sites, with Yellow Rock the only site where pups have not been observed. This is traditionally a male dominated haul out with few females being observed at this site. Conversely, we have seen the highest number of mum pup pairs at the nearby Muller Island site, observing up to four pairs hauled out in close proximity to each other, almost like a nursery! It’s interesting watching the pup behaviour, resting, suckling, and swimming and attempting to keep up with mum.

Now that some of the pups are two to three weeks old it’s noticeable how their confidence is growing and they’re entering the water alone more, with mum leaving them alone for longer periods of time. It is not long before they will be weaned and separate from mum completely!

A mum and pup pair photographed at Southend. Right after this the pup went for a lone swim while Mum watched from on land! (photo: Emily)

The pupping season is well under way in Orkney. The first pups we saw this season (just before mid June) are now almost 3 weeks old. We have not seen any more pregnant females in the last couple of days, so it is likely the majority of the pups have been born. The last two females that have given birth are two seals known to the project. One of them is Or026, which was first photographed in 2014 as an adult, as part of a separate project. A scar between the eyes makes her very recognizable, even though she has fairly pale pelage, especially around the head.

Or026 has a scar between the eyes that is easy to spot! We have nicknamed her “pirate”.

Or026 was seen in Widewall Bay (South Ronaldsay) at a small haulout site, but we had expected to see her in Burray, where she was mostly seen for the last couple of summers. The sightings in Widewall Bay made very obvious that she was pregnant, given her size and the extra belly.

Or026 (top seal) resting in Widewall Bay on June 7th

She was seen again on the 28th of June, this time in Burray in a haulout site that is generally used before the pupping season, but it seems that females (and males) move then to a close-by site for pupping. That day she still looked fairly big, although it was hard to tell given her position. Then, she showed up at the main pupping site the following day with a brand new pup!

Or026 and her new pup checking on me while playing among the seaweed

The other female that gave birth recently is Or085, which is known to the project since 2016 and was one of our females carrying a telemetry tag last summer , which we used to investigate the movements and diving behaviour previous and during the pupping season. We know that this female was 5 years old in 2016 when she had a pup, which we think could have been the first time. This year, aged 6, she has had a second pup. She was seen pregnant on June 28th on a very hazy and hot day in Burray, and then showed up at the haulout site where most of the mum-pup pairs are found on July 1st with her pup. You can clearly see the pup still has the umbilical chord attached!

Or085 looking pretty big on June 28th. She kept changing position, which we often observe in largely pregnant females.

Or085 with her pup! Check the umbilical cord.

With so many pups, plus all the mums, other females, juveniles and males, the haulout sites are quite busy. To that you just need to add some grey seals wanting to haulout very close, and there is trouble! On the positive side, that offers good opportunities for photo-identifications, as good pictures of both the right and left side of a seal can quickly be taken.

The photoID season in Orkney started a couple of weeks ago, just before the start of June. Having been away from Orkney since last August, it was nice to recognize the seals and start seeing heavily pregnant females at the monitored haulout sites.

Female Or038 from the Orkney catalogue showing a large pregnant belly

Despite seeing familiar faces, the numbers of seals at the different haulout sites around Burray and Widewall Bay were lower to start with compared to last year. After a few days of low counts I discovered a bunch of seals resting at some more distant skerries. They were too far for me to take good photo-ID data but it was good to see that the numbers were not that low after all!

A bit too far for photoID unfortunately!

The sun has been mostly shining in Orkney, which sometimes is not ideal when taking photographs of sleeping hazy seals, as Izzy has found out in Kintyre too. Before the pups arrive, the dynamics at the haulout sites can be fairly calm, as once all seals have found the perfect spot to rest, it’s snooze time.The key is to have patience and wait for the seals to change position as the tide advances or wait for them to lift their heads. Even though we could potentially use any part of their pelage for identification, we focus on the face, from both sides and from the front, as that is the easiest part to photograph consistently for all seals.

Sunny days call for long sleeps at the haulout site, perfect for these pregnant females!

The start of this week brought a nice surprise with the first pup of this season in Orkney! The pup belongs to a female from the catalogue, Or038, which we first photographed in 2016. The mum-pup pair were seen at the haulout for a bit while the pup suckled and then went into the water where they were seen interacting very close by, with frequent nose-to-nose contact, and the pup managed to ride on mum’s back when heading away.

Or038 with her pup in the water

Nose-to-nose contact before some suckling time

The following day we managed to spot the same mum-pup pair at a nearby haulout site. Because pups are born with their adult coat, each pup already has a unique pelage pattern, which allows us to identify each pup and follow them through the season. I suspect the number of little ones will start to increase from now on, given the sightings of heavily pregnant females at the haulout sites. We will be making notes and taking photographs of all mum-pup pairs through the season, which will help us determine the birth rates at each of the study sites.

The first week of photo ID fieldwork for the Harbour Seal Decline Project has got off to a flying start here in Kintyre. Despite the persistently sunny days making it hard to get good photographs through the haze and glare, we have seen our first pup of the season!

The first mother and pup pair for Kintyre 2018

This is about a week earlier than last year, and the pup looks quite premature as it still has some of its white, lanugo coat which is normally moulted off in the womb. Nevertheless, the pup seemed full of life, swimming with its mum in the shallows.

The mother and pup pair were spotted at Muller Island, where the northern site has had an average of 15 adults hauled out at low tide every day this week. The southern site at Muller Island has seen similar numbers, gradually increasing as the week progressed.

Another site we are monitoring this season, also overlooking Ardnacross Bay, is Yellow Rock. The seals here at high tide haul-out within 50m of the beach which makes our job infinitely easier. The bay has been so calm and still this last week that we can almost do photo ID from the reflections in the water!

Reflection of a male harbour seal in the water at Yellow Rock

Along with the seals, we have had some great bird sightings, including a Great Northern Diver and a group of Red Breasted Mergansers. There have also been rumours of a pod of bottlenose dolphins traveling up the east coast of Kintyre so we’ll be keeping a look out for those!

A Great Northern Diver, spotted at Seal Rock

As much as it pains me to say it, we will be hoping for some less sunny days over the next few weeks to ensure we get the data we need for the project. If this is the case, in the next blog post you’ll no doubt hear me complaining about the midges!

After a long break over the winter months, we are back to update on the blog as the new photoID season approaches at a very fast speed. We have spent the winter months processing the thousands of photographs collected in 2017 as well as tidying up the 2016 data. Because 2016 was our first year of collection, the workload was considerable given that we had to build the seal catalogues for each study site from scratch. Now that the photoID catalogues are built for each area, the processing of new photographs is a bit quicker. Also, we have been testing different recognition software to help us match seals. Keep an eye on this space for an update on how we use these.

Harbour seals at Peninver

Like last summer, our colleague Andy Law will be heading out on the boats that leave from Dunvegan Castle (Isle of Skye) to photographs the seals hauled out in the skerries of Loch Dunvegan. I personally will be heading up to Orkney in a week to start monitoring the selected haulout sites in Burray and Widewall Bay. The Kintyre sites will be monitored by Izzy Langley this year. Ahead of the pupping season, last week we took a short trip to Kintyre to check the haulout sites and explore how these change through the day with the tide to figure our when and from where is best to photograph seals. We were lucky to have Craig with us to show us around, and give us the best tips based on his experience monitoring the sites for the last couple of years.

Ardnacross Bay

After a nice but long drive we arrived at sunny Campbeltown in the late afternoon, in time to have a quick look at a couple of the haulout sites. The first one was in Peninver, and even though the tide was really high we found a nice group of seals resting on some exposed rocks very (VERY) close to the shore. It was very interesting to see how those seals, who are used to having people walking nearby were used to our presence, showing no signs of being disturbed. This apparent habituation of the seals to people walking nearby tends to be the exception more than the norm. Seals are generally vigilant when onshore, and tend to get easily disturbed when people get into close proximity. That is why it is so important to keep a distance and a low profile when approaching haulout sites to avoid disturbing the seals.

Having a close look to the seals at Peninver Sands

We also headed up a bit further north in Ardnacross Bay to check on a haulout site that tends to be busy during the summer. Given that it was high tide there were no seals around except in the water, but it was a good opportunity to check on the access to the site.

The next morning we woke up early and headed straight to the remaining haulout sites while the tide was low. We found a small group of seals hauled out at Muller Island, for which the observation point is set up very nicely at an elevated grassy path that allows us to observe and photograph the seals without causing any disturbance. We made a note that some of the females were obviously pregnant, showing extra round bellies.

Seals at Muller Island in Kintyre

To finish off the morning we headed south to the tip of the Kintyre peninsula, where another small group of harbour seals tends to rest during low tide. In there we found a mixed group of harbour seals of different age classes, including some pregnant females and a couple of juveniles. Izzy will be going back to these haulout sites during June and July to document all seals, with special interest on the mum-pup pairs. I wonder which site will have the first pups?

Once again we are approaching the end of our photo-ID effort at the study sites. Following last year’s pattern, the mood at the haulout sites in Orkney has considerably changed over the last couple of weeks. Most of the pups have been weaned which means the females are free to go foraging before they start moulting.

Pup suckling at one of the haulout sites in Orkney

Pup making the most of the fat-rich milk before weaning time arrives

The haulout sites are now filled with the newly weaned pups, some of which are not quite over the fact that the good days of suckling the fat-rich milk are over. If the opportunity shows, they will try to get some extra feeds from the few females that are still suckling their pups. Despite their best efforts, they tend to get discouraged fairly quickly either by the females or by the pups holding the right to suckle. In the video below you can see a female coming to shore followed by three pups, two of which are just wanting that extra feed. However, they quickly realize that’s not going to happen and go back into the water.

On some occasions females seem to tolerate the presence of a second pup and might allow it to rest near by, but again, that doesn’t last long if the pup attempts to get too close. That’s exactly what seems to occur in the next video, also captured in Orkney. This female came onshore with two pups and started suckling one (assumed to be hers) while tolerating the presence of a second one of similar size. However she quickly snapped that pup to presumably stop it from approaching any further.

To better understand whether this phenomenon is down to just a few pups or is more widespread, we do try to get pictures of the pups as well as the adults. Because pups are born with their adult coat, they already have a characteristic and unique pelage pattern. By identifying pups we can attempt to estimate how long are pups seen in association with their mothers, how long does the lactation period last and whether pups will suckle from different females.

Female Or098 with her pup on 14th July 2017. This wee guy has a wishbone mark on his left cheek!

Or098’s pup on its own on 16h July 2017. The same wishbone mark can be seen in the pelage pattern on his left cheek.

As pupping season comes to an end, preparations for mating and moult season are well underway. Some of the bigger males have been seen more regularly at the haulout sites in Orkney and have offered all kinds of displays. These go from simple grunting exchanges with other males in the distance, to fast swimming along the haulout sites, throwing seaweed around, as well as proper physical fights. In the next video we captured two harbour seal males fighting; the younger one (smaller) had been warming up by doing the seaweed throwing as well as grunting, and got even crossed with an unfortunate pup that was at the wrong place at the wrong time. Luckily it was all just a big scare and the pup managed to haulout and recover from the unwanted fight. However, the young male kept on challenging a much bigger male, until they started to fight. After a resting period, they both took it back into the water, where full body flips and jumps were seen from the distance. After that, they both rested on land, like nothing had happened.

While the adult males are busy maintaining territories and fighting with other males, some of the younger seals are well into their annual moult, while other adults are just starting it off. The first seals to moult are those with the oldest coat, which will be the pups born last year, as well as the very young seals that also moulted early last year. The old hair is brown and in patches, but the new coat showing underneath displays gorgeous and distinctive black and white patterns. The moult period is an itchy one, and seals can be seen scratching themselves as the old coat gets slowly replaced by the new one. Is in this time of the year when seals spend a higher proportion of time hauled out onshore rather than in the water. The moult is an expensive period in terms of energy, as warm blood is circulated very close to the skin to help the new hair grow quickly. To avoid losing energy by getting cold in the water, seals spent much more time onshore.

Adult harbour seal starting to show signs of the annual moult

Moulting male harbour seal; all the old brown hair will fall and be replaced by the new coat

This young female is already showing her new coat around the head and shoulders

For the last three weeks I have been a very busy bee in Orkney, hence the delay on updating the blog! The pupping season is advancing with giant steps, pups are getting bigger every day, some others have already been weaned and adults are showing the first signs of the annual moult!

The weather has mostly been on our side with overcast and slightly breezy days, which make photo-ID a much easier job. However, we’ve had our share of sunny and calm days, which make photo-ID a tricky business as the seals look all hazy through the lens and the pelage patterns are really difficult to identify. And there is always the risk of unwanted midges company! Very wet and windy days also pose a challenge as it’s hard to keep the equipment dry and safe.

Sunny and calm day in Orkney = photoID with 10,000 midges.

A couple of weeks ago I spotted a grey and a harbour seal having a nice rest on a hot and sunny day, both with a telemetry tag on. The grey seal was tagged as part of a separate SMRU project, which is collecting data for the Met Office. Grey seals are often seen sharing the same haulout sites as harbour seals, although haulout sites of only grey or harbour seals are also the norm. In Orkney, all the of the monitored haulout sites where we collect photoID data are mainly harbour seal haulouts, but grey seals are also found in smaller numbers. In Loch Dunvegan (Isle of Skye), where Andy collects photoID data, it’s very rare to have grey seals sharing the same skerries, but sometimes there is the odd grey seal that shows up.

Grey and harbour seal tag buddies on a hazy day

Grey seal with a telemetry tag on one of the monitored haulout sites in Orkney

Grey and harbour seals have different haulout behaviours. While grey seals seem to be ok hauling out very close to each other, harbour seals prefer to keep a larger personal space around them. If another harbour seal or a grey seal comes too close, they start grunting and moving one of their foreflippers to keep the approaching seal away. Harbour seals will rather get back into the water and find a quieter space than staying too close to a curious grey seal!

Harbour seal looking rather unhappy with an approaching grey seal…

Two grey seals having a snooze at a haulout site in Orkney with harbour seal neighbours

In general grey seals will haulout and rest, but in some occasions some other action can be seen. Sometimes younger grey seals will curiously approach harbour seal pups, or simply stir the tranquility of the haulout by walking through the grey seal haulout, starting a sequence of loud and characteristic grey seal hauling. Last month, as I was taking pictures in Widewall Bay, in South Ronaldsay, I filmed a couple of grey seals playing-fighting at one of the haulouts. In my limited experience with grey seal behavior it looked like a male grey seal playing with a female and making a rather poor attempt at mating.

Despite our main interest being harbour seals, one cannot miss the other wildlife sharing the haulout sites, starting with the many species of birds that can be regularly seen. Black-backed gulls and great skuas patrol the haulout sites in search of a free meal. At the start of the pupping season large groups of greylag geese can be seen at or flying past the haulout sites, generally in a rather noisy way! Oyster catchers and curlews add to the sound track, very often giving away my hiding spot to the seals. At one of the study sites, which sits below a cliff, the seals are accompanied by the constant chatter from fulmars nesting nearby. Redshanks and ringed plovers can be seen on the sandy and pebble shores close to the water, and herring gulls can be often seen walking around the seaweed covered rocks by the water. It turns out they like to eat sea stars!

Ringed plover at one of the haulout sites

Herring gull eating on a sea star

As the summer advances, larger groups of arctic terns are making an appearance at two the the monitored haulout sites, the larger being in Widewall Bay. A couple of weeks ago there was such a large group of them that they frequently photo-bombed my photo-ID effort. I don’t think the seals were very happy with such noisy neighbours!

But it’s not all birds among the neighbours… there are also some more infrequent visitors. Last week we had a surprise visit from an otter! She was seen swimming past the haulout site and ended up coming up on shore to undergo a good clean up. She then had a quick rest before going back to the water. I was lucky enough to be close by without being spotted and the digiscope system we use to get photoID data did the rest… check the picture and video below.

Otter spotted near one of the haulout sites in Burray

And finally, another marine mammal that can make an appearance is the killer whale. Killer whales are natural predators to seals, and are regularly seen around Shetland, Orkney and the north coast during this time of the year. I have personally never seen them nearby the haulout sites we monitor, but have seen them in other areas around mainland. Public sightings report them frequently in the Pentland Firth between Orkney and mainland, but also in the waters around Birsay. While going for a walk along Rerwick Head, at the north side of mainland, we were lucky enough to bump into a group of 5 killer whales that were swimming very close by the shore. After the initial excitement we managed to capture them passing by, see the video below. The group seemed to be composed by 1 male and 4 females or juveniles, the male having the very tall and straight dorsal fin. I seemed to recognize one of the females as Mousa, a female killer whale that is regularly seen in Shetland and Orkney waters. This female is also included in the catalogue of killer whales from Iceland (with ID number IS086). Like Mousa, some other individuals repeatedly move between Iceland and Scotland. These whales appear to feed on the Icelandic summer-spawning herring stock in the winter, and then move outside the summer distribution range of this herring stock (check more details on this published paper on the matter). More information on the Icelandic orcas can be found in their website and in their Facebook page

The end of June marked the half way point on our photo-identification effort during this year’s pupping season. At least at the monitored haulout sites in Orkney, all females seem to have given birth, as I cannot observe obviously pregnant females anymore. For what Craig tells me, he is still observing a few pregnant females in Kintyre ready to give birth. After all, he was the last one to observe the first pup this year. As for Isle of Skye, Andy has been going our regularly with the boatmen from Dunvegan Castle when the weather has permitted, and has had really good days counting around 130 seals hauled out and 34 pups seen! At the haulout sites in Orkney, numbers are much lower, with around 40 adult seals and 20 pups seen on average at the main pupping site.

Several mum-pup pairs in Orkney, well camouflaged!

With all the new pups around, the haulout sites are busy places. Pups seems to have their own agenda, going into the water quite often and consequently dragging mum behind. When not suckling or sleeping they are curious individuals and will explore their surroundings and neighbors. Other pups seem to be ok with other little ones approaching, unless they are getting too close to their food provider. Some adults tolerate pups that just get close to have a nice spot to rest, but will get rather annoyed with with pups that approach too close, especially if they are after suckling from females other then their mothers. Yesterday I came across a mum pup pair that hauled out right next to another two pups on their own. One of them came closer to inspect, until he got too close and got a grunt from the female (see photograph below).

Lonely pup (back) staring at another pup suckling

Pup climbing over his mum soon after hauling out

After suckling, some pups go straight onto having a nice nap, while others like to move and play around for a bit, like this one:

At this time in the pupping season, it is normal to observe pups on their own. Female harbour seals will go on short foraging trips during this time, and come back shortly after to suckle their pup. While this is normal for seals, it makes photo-ID life a little bit more complicated as it becomes a bit more difficult to link pups and adult females. Patience is definitely a key element. Sometimes pups left on their own will fall asleep totally unaware of what the tide is doing. When they fall asleep while the tide goes down they then wake up rather far away from the water, as it happened to this pup:

Lonely pup waking up rather far away from the water’s edge!

On a couple of occasions I have witnessed female harbour seals accompanied by two different pups. While twin births are rather rare in seals, fostering is a more frequent event. Sometimes inexperienced mums which might have had their first pup will get confused at a second pup approaching and will allow it to suckle. If a pup gets abandoned to somehow separated from its mum, it will try to suckle from other females. In both occasions, one of the pups seemed to be of smaller size and weight than the other one, which makes me think it was an abandoned pup not feeding as much as needed. In both cases the female seemed to be snappy at times with the second pup and at the end left into the water with just the bigger pup. Having to suckle a second pup is likely to have a detrimental effect on the survival probability of both pups, as resources have to be split and they might not put enough weight before getting weaned. At the same time, it might also have a negative effect on the female’s fitness condition at the end of the pupping season, potentially having had to use more energy resources than anticipated and potentially compromising her fitness for the next steps in her yearly cycle.

Female harbour seal with two pups. The one on the right was obviously much smaller than the other one. Both pups managed to suckle from this female.

A different female harbour seal with two pups again. After suckling the pup on the left, the female ended up swimming away with the pup on the right, which looked bigger.